44 lines
1.1 KiB
Solidity
44 lines
1.1 KiB
Solidity
// SPDX-License-Identifier: MIT
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pragma solidity ^0.6.0;
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import "./ERC20.sol";
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/**
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* @dev Extension of {ERC20} that adds a cap to the supply of tokens.
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*/
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abstract contract ERC20Capped is ERC20 {
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uint256 private _cap;
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/**
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* @dev Sets the value of the `cap`. This value is immutable, it can only be
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* set once during construction.
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*/
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constructor (uint256 cap) public {
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require(cap > 0, "ERC20Capped: cap is 0");
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_cap = cap;
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}
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/**
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* @dev Returns the cap on the token's total supply.
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*/
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function cap() public view returns (uint256) {
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return _cap;
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}
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/**
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* @dev See {ERC20-_beforeTokenTransfer}.
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*
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* Requirements:
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*
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* - minted tokens must not cause the total supply to go over the cap.
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*/
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function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual override {
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super._beforeTokenTransfer(from, to, amount);
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if (from == address(0)) { // When minting tokens
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require(totalSupply().add(amount) <= _cap, "ERC20Capped: cap exceeded");
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}
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}
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}
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